#define _CRT_SECURE_NO_WARNINGS 1

#include <stdio.h>

int main() {
    int n = 0;
    scanf("%d", &n);
    int i = 0;
    int tmp = 0;
    int ret = 0;
    for (i = 0; i < n; i++)
    {
        scanf("%d", &tmp);
        ret ^= tmp;
    }
    printf("%d", ret);
    return 0;
}